pH-Dependent Assembly and Conversions of Six Cadmium(II)-Based Coordination Complexes

Six cadmium(II) complexes containing the N2O2 donor tetradentate asymmetrical Schiff base ligand 2-{[2-(dimethylamino)ethylimino]methyl}-6-methoxyphenol (HL5), namely, [(Cd3L5 2Cl4)2]·CH3OH·H2O (1), [Cd(L5)Cl]2·CH3OH (2), [Cd2(HL5)Cl4] n (3), {[Cd3(H2L5)2Cl8]·2H2O} n (4), [(H2L5)2]2+·[CdCl4]2−·H2O (...

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Bibliographic Details
Published in:Crystal growth & design 2010-07, Vol.10 (7), p.3277-3284
Main Authors: Fang, Hua-Cai, Zhu, Ji-Qin, Zhou, Li-Jiang, Jia, Hong-Yang, Li, Shan-Shan, Gong, Xue, Li, Shu-Bin, Cai, Yue-Peng, Thallapally, Praveen K, Liu, Jun, Exarhos, Gregory J
Format: Article
Language:English
Subjects:
CADMIUM
CADMIUM COMPLEXES
CHEMISTRY
CHLORIDES
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Exact sciences and technology
MATERIALS SCIENCE
MOFs, Structural Transformation
Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation
PH VALUE
Photoluminescence
Physics
SCAVENGING
SCHIFF BASES
SENSITIVITY
TRANSFORMATIONS
WATER
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Summary:Six cadmium(II) complexes containing the N2O2 donor tetradentate asymmetrical Schiff base ligand 2-{[2-(dimethylamino)ethylimino]methyl}-6-methoxyphenol (HL5), namely, [(Cd3L5 2Cl4)2]·CH3OH·H2O (1), [Cd(L5)Cl]2·CH3OH (2), [Cd2(HL5)Cl4] n (3), {[Cd3(H2L5)2Cl8]·2H2O} n (4), [(H2L5)2]2+·[CdCl4]2−·H2O (5), and [(H2L5)2]2+·[CdCl4]2− (6), have been synthesized using cadmium(II) chloride and the asymmetrical Schiff base ligand HL5 under different pH conditions at room temperature. The diverse structures show the marked sensitivity of the structural chemistry of the tetradentate asymmetrical Schiff base ligand HL5. Complex 1 formed at pH = 10 exhibits a rare zero-dimensional structure of trinuclear cadmium(II). At pH = 8−9, a dinuclear cadmium(II) complex 2 is formed. The reaction at pH = 5−7 leads to two one-dimensional structures of 3 and 4. A further decrease of the pH to 3−5 results in a zero-dimensional structure 5. Owing to the departure of lattice water molecules in the crystal, complex 5 at room temperature can gradually undergo single-crystal-to-single-crystal transformation to result in complex 6. The results further show that conversions of complex 1−5 can also be achieved by adjusting the pH value of the reaction solution, 1 → 2 pH=8 → 5 pH=3 and 3 → 4 pH=5. Comparing these experimental results, it is clear that the pH plays a crucial role in the formation of the resulting structures, which simultaneously provides very effective strategies for constructing the CdII compounds with N2O2 donor tetradentate asymmetrical Schiff base ligand. The strong fluorescent emissions of the six compounds (1−6) make them potentially useful photoactive materials. Furthermore, six Schiff base cadmium complexes (1−6), with 2,2-dipheny1-1-picrylhydrazy1 (DPPH) as a co-oxidant exhibited the stronger scavenging activity.
ISSN:1528-7483
1528-7505
DOI:10.1021/cg1004598